High-power luminous electrical discharge tube



Jan. 13, 1931. w. F. HENDRY HIGH POWER LUMINOUS ELECTRICAL DISCHARGETUBE 19. 1927 3Sheets-Sheet 1 Filed Dec.

INVENTOR ATTORNEY Ill/l Jan. 13, 1931. w. F. HENDRY HIGH POWER LUMINOUSELECTRICAL DISCHARGE TUBE s SheerQs-Sheet 2 Filed Dec. 19, 1927 INVENTORATTORNEY 55:5.Eiiifiiitat W an Le a @013 I q 1 A Q Jan. 13, 1931. w. F.HENDRY HIGH POWER LUMINOUS ELECTRICAL DISCHARGE TUBE Filed Dec. 19, 19273 Sheets-Sheet 3 ATTORNEY Patented Jan. 13, 1931 v UNITED sTATEs PATENTOFFICE WILLIAM F. HENDRY, OF OSSINING, NEW YORK, ASSIGNOR, BY MES NEASSIGNMENTS, TO MANHATTAN ELECTRICAL SUPPLY COMPANY, INC., 01' JERSEYCITY, NEW JERSEY, A CORPORATION OF NEW JERSEY v men-rowan LuminousELECTRICAL DISCHARGE 'runn Application filed December 19, 1927. SerialNo. 241,062.

This invention relates to gas filled electrical discharge tubes andrelates more particularly to that type of tube wherein light is producedby the passage of an electrical discharge. be- 5 tween a pair ofelectrodes positioned in an atmosphere of a gas such as one of the raregases, e. g. neon, contained within a llght transmitting envelope suchas glass or the Electrical discharge tubes of this type have been knownfor many years and many and varied structures have been provided inorder to secure the best results possible from these tubes. Diflicultyhas been experienced in is preventing the attenuation in the gaseousatmosphere of such tubes and even so when the atmosphere consisted ofone of the rare gases such as neon; The main reason for this attenuationof the gaseous atmosphere appears to have been because of the sputteringof the material forming the electrodes of the tube. This sputtering orprojecting of particles of electrode material from the surface of theelectrode apparently causes an occlusion, entrapment or absorption ofthe gas in the tube in such manner as to lower the pressure of r thetube, and after a period of time to render the tube useless. Variousmethods for main taining the pressure of gas within a tube conso stanthave been proposed] One of the first of these probably consisted inproviding an auxiliary reservoir of the gas utilized in the tube andinterconnecting this reservoir with the tube through an automaticallyoperated valve )5 which served to admit gas whenever the pressure of theatmosphere within the tube became reduced below the desired operatingvalue. It has also been proposed to make the surface of the electrodess'ufliciently large so that current density of the electrodes will besmall, preferably below'one ampere per 1% square decimeters of activeelectrode-area, as stated in Patent No. 1,125,47 6, issued to GeorgesClaude. 1

While the gaseous tubes ofthe type above referred to have manyadvantages it has been difficult in the past to secure suflicientlyconcentrated illumination, thatis to say, in order to get a given amountof light it has been found necessary to make the light source ofrelatively lar e area; However, attempts have been mania (seeProceedings of the German Physical Society, pages 145-156, 1910) toincrease the intrinsic brilliancy of special tubes, by increasing thecurrent density of the gas column thereof. These experiments involvedthe use of electron emitting cathodes of the Wehnelt type. By usingelectron emitting cathodes of the type above mentioned, it was foundpossible to produce'a sort of arc-like discharge of such intensity thatitwas attempted tokeep the glass walls of the tube from damage byplacing the tube in a vessel of Water. In such tubes, the cathodes wereso large and required somuch heating current that, in order to withstandthe heat generated thereby, it was necessary to make the tube of suchvery large dimensions as to be very inconvenient. A further disadvantagewas that the cathodes frequently burned out. Other types of tubes havingelectron emitting cathodes have been made also, with a view of making alow voltage, high intensity light. These tubes were especially adaptedto operate on direct current. Tubes of the type referred to in thesecond proceeding paragraph are used to a large extent for the making ofluminous signs wherein the sign letters or symbols are formed by a gasfilled glass tube containing electrodes between which an electricaldischarge is caused Y to pass. As these signs are exposed to the weatherit has been found that the glass tubing forming the lamp is liable to becracked due toviolent changes in the temperature thereof, that is tosay, when the tubes are operated at sufliciently high current densitythey become so hot that when a vcold blast of Winter air or snow strikesthem that the glass is liable to be broken due to the swift change intemperature. This difliculty limits the brilliancy of this type ofluminous tube.

One object of my invention is the provision of an electrical dischargeilluminating tube capable of operation in such manner as to produce anextremely brilliant and concentrated light suitable for use such assignal lamps, aeroplane beacons and the like, and susceptibleofdirectivemeflection similar to a Searchlight.

light'emitted therefrom. In this manner I tion from a tube of smalldimensions.

Another object of my invention is the provision of a tube structurewhich permits of the passage of current at high density withoutsubstantial attenuation of the gaseous atmosphere and 'withoutdestruction of the lead-inwvire seal or other parts of the tube. 1 Stillanother object of my invention is the provision of a luminous electricaldischarge tube so constructed that it is maintained at a constant lowtemperature even when operated at extremely high current densities.

Another object is the provision of a luminous electrical discharge tubecapable of producing an intensely brilliant light, without the use ofoxide coated electrodes or other electrodes especially adapted to emitelectrons.

I have found that the sputtering of the -material forming the electrodesof an electrical discharge tube of the type above described canmaterially reduced by maintaining the electrodes sufficiently cool.Where an electrode is used for extremely heavy duty at high currentdensities Iobtain this result.

by circulating a cooling fluid such as water, oil, or the like,-throughthe inside of the electrode, which is made hollow. While water may befound preferable for use as a cooling fluid on account of its abundanceand low cost, it is to be understod that other cooling fluids can beused as'well, depending upon the intensity ofthe gaseous discharge andupon the particular operating conditions. Where a tube does not have tooperate at extremely high current density it is possible to reduce thesputtering of the electrodes by making the electrodes of massive formand surrounding them with heat conducting material which serves toconduct the heat from the electrodes to the walls of the envelope withinwhich they are enclosed, as set forth in my copending application,Serial No. 180,788, filed April 4,1927. The water cooling of theelectrodes permits such a large amount of current to be passed throughthe tube that the temperature of the glass wall may be raised to such adegree that it would be melted or otherwise damaged. In order" toprotect the wall of the tube against such damage I provide a jackettherefor so that the temperature of the tube can be kept constant by thecirculation of cooling water. By maintaining the wall of the tube cool Iam able to pass an extremely large amount of current through a tube ofsmall size and thereby greatly increase the brilliancy. of the am ableto secure a large amount of illumiIKis stated above, it has heretoforebeen thought necessary inorder to pass a large amount of current througha body of gas such as neon, to provide electrodes of extremely largearea. The reason for this was that when it was attempted to pass largeamounts of current through a tube the electrodes ofthe tube sputtered.so violently that they were destroyed or the gaseous atmosphere wasattenuated sufiiciently to prevent the tube from working. The reason forthis sputtering of the electrodes was not fully understood and wasthought by some investigators to be due to some obscure phenomena,possibly to bombardment of the electrodes by positive parti-' cles. Itwas accepted that thc sputtering of the electrode material wasproportioned to the current density of the operating area of theelectrode andon the basis of this theory it was suggested that toprevent sputtering of the electrodes and attenuation of the gaseousfilling thecurrent density at the active electrode surface be reduced toone ampere per 1.5 square decimeter of active electrode area. However, Ihave found that by cooling the electrodes 'sufliciently it is possibleto pass a large amount of current'through a gas column using relativelysmall electrodes and thereby increase the intrinsic brilliancy of thelight emitted.

By cooling the electrodes and thereby preventing excessive sputtering Iam enabled to operate tubes having an initial gas pressure as low as tenmillimeters ovena long pe- IlOd of time without excessive attenuation ofthe gaseous atmosphere.

While it is possible to construct gas filled tubes which will operatesatisfactorily for a period of time, using an active electrode area of1.5 square decimeters per ampere of discharge current in accordance withthe teachngs of the above mentioned Claude patent, it has been foundthat to construct a commercial tube capable of operating satisfactorilyover a relatively long, period of time, it is necessary to provide anactive electrode area of around 14 square decimeters per ampere ofdischarge current, and to use 'a gas pressure -in the neighborhood of 14millimeters. I

have found that by constructing a tube having cooling means inaccordance with my invention that it is possible to utilize an activeelectrode area of but 1.5 square decimeters per ampere, or even less,and a gas pressure of about 10 millimeters, and still secure acommercial form of tube capable of operating satisfactorily over arelatively long period of time.

In order further to increase the brilliancy of the light I find itdesirable to use a gas column of relatively small cross section ascompared to the size of the electrodes, as this permits the currentdensity to be raised still higher. This is accomplished by making thegas containing tube small and coiling it in the form of a helixsimilarly to a spring, so that while the length of the gas column isgreat, the over-all length of the light emitting surface is relativelysmall.

These and other objects and advantages and the manner of obtaining themwill be 7 more particularly described in connection with theaccompanying drawings.

In the drawings Fig. -1 illustrates a half wave tube constructed inaccordance with mv invention.

ig. 2 illustrates a special form of water cooled electrode.

Fig. 3 illustrates a tube having a water cooled gas column without watercooled electIOdGS. I

Fig. 4 shows a modified form of tube structure.

Fig. 5 illustrates a portion of a tube of modified construction.

7 5' In the drawings, reference numeral 1 indicates an illuminating tubecomprising apair of electrode chambers 2 and 3 interconnected by aspiral formed gas containing tube 4 which is positioned within anenlarged tube 5 5 welded to walls 8 and 9 of the said electrodecontaining chambers. This tube 5 is provided with two nipples 6 and 7through which water can be forced through the tube. Within the electrodechambers 2 and 3 are posi- 25 tioned electrodes 10 and 11 respectively.The electrode structure 10 is of the same general type as that disclosedin my said copending application Serial No. 180,788, wherein the innerelectrode point may consist preferably of a conductor such as copper,aluminum or the like and is made hollow in such manner that acoolingfluid can be circulated therethrough by means of a pair of pipes 12 and13 attached thereto. These two pipes 12 and 13 are sealed through thewall'of the tube 1 at 14 and 15 by means of a balsam of fir seal of thet pedisclosed in my copending application erial No. 213,592, filedAugust 17, 1927. These pipes 12 and 13 are preferably 40 formed intoloops such as 16, in order to provide for any variation in length due tothe expansion or contraction of the parts of the tube due to change intemperature. The electrode structure 10 consists of an alongated pointelectrode 23 having a sleeve of heat resisting insulating material 24positioned therearound and secured against movement by means of pins 25which project through the sleeve into the electrode body. The sleeve 24is provided with a flange 26 which serves 'to center the electrodestructure in the tube and also serves to retain in position a quantityof glass wool or similar material 27 which is placed between the tubewall and the elec- 5 trode assembly. Surrounding the sleeve 24 is a tube28 of Pyrex or other heat resisting material between which and thesleeve wall more glass wool is packed.

During the exhaustion and gas fitting of the tubea discharge is passedbetween the electrodes, while no cooling water is passing therethrough,in such manner that the electrode 23 is heated very hot for the purposeof degasification, etc. The heavydischarge between the uncooledelectrodes tends-to strike back around the base of the electrode unit 10and damage the seals. The function of the glass wool is to prevent thisstriking back. As the electrode 23 is heated to a very high temperaturethe tube\25 is provided to o prevent melting of the glass wool 27 by in;

sulating it from the direct action of the heat of the electrode.

Electrode 11 is constructed in the form of a double wall cylinder havingits two walls closed together at the ends to make a tight enclosurewithin which cooling water may be circulated by a pair of pipes 19. and20 which are connected to the electrode ll and sealed through the wallof the tube at 21 and 22 in the same manner as tubes 12 and 13 ofelectrode 10. This electrode is provided with spacing beads 29 which areplaced in :1. groove in the outer surface of the electrode. Theconstruction of the gas filled tube 4 in the form of a helix preventsbi'eakage of the tube due to expansion and contraction upon a change intemperature thereof and breakage due to shock or vibration, by insuringgreater resiliency thereof. A tube constructed in helical form, asdisclosed, can be subjected to severe vibration and abuse without damagethereto, as any shocks or strains due to change in temperature are takencare of by expansion and contraction of the glass helix. The tube isadditionally protected against damage due to vibration by the coolingfluid which surrounds the glass helix, the fluid serving to damp out thevibrations of the glass helix and prevent violent movements thereof. InFig. 2 is illustrated another form of water cooled electrode 30, whichis extremely easy and cheap to construct and which works efiiciently.This electrode consists merely of a pipe made of copper or otherconducting material wound in the form of a double helix which may bespaced from the tube walls by means of insulating beads 29 similarly toelectrode 11 of Fig. 1. I prefer that the electrode be wound in the formof a double spiral as if it is wound in the form of a single helix andthe return pipe passed down in the center-of the helix the return pipeis subjected to more violent electrical action due to the fact that themajor portion of the discharge takes place within the interior of ahollow cylindrical electrode. The return p ipe might be run down outsidethe helix, but by making the electrode in the form of a double helix allparts of the elpctrode are subjected to uniformly low strain.

The tube illustrated in Fig. 3 is substantially similar to thatdisclosed in Fig. 1 except that the electrodes are not water cooled butare preferably packed with glass wool or a similar heat conductingmaterial 33, in the manner disclosed in my said copending applicationSerial No. 180,788. This type of tube is not adapted to extremely heavycontinuous duty but may be used for nioderate-1y heavy continuous workor heavy intermittent work such as flashing for advertising orsignalling purposes.

In Fig. 4 is illustrated a modification of the water cooling arrangementfor the gas column. In this arrangement a water carrying tube 31 ispositioned within a slightly larger gas filled tube. The gas column inthis case presents a large surface area despite the fact that the.current density thereof is kept high due to the small cross sectionalarea of the gas column.

The structure shown in Fig. 5 may be found more easy to construct thanthat of the other figures and may be used interchangeably therewith. Asshown in this figure the two electrode chalnbers 2, '3 areinterconnccted with the center section of the tube 1 by means of tubes34. which are tapered down and joined to the helical tube 4 in suchmanner as to form continuations thereof. It is easier to weld the centersection of the tube to the tubes 34 than directly to the electrodechambers 2 and 3.

\Vhile I have illustrated the tube shown in Fig. 1 as a single wave orrectifying tube, it will be understood that a full wave or nonrectifyingtube may be constructed in like manner. that is. such a tube might bemade with both electrodes constructed similarly to electrode 11 orsimilarly to electrode 10.

One very great advantage obtaining from the use of water cooledelectrodes constructed in the manner which I have outlined above is thatwhen the electrode and its seal is kept at sufliciently low temperaturethe tube can be operated at relatively high voltages without danger ofelectrical breakdown of the insulating material supporting theelectrode. It is well known that in an ordinary type of tube when toogreat a potential is applied to the terminals. the discharge shows atendencv to strike down over the surfaceof the electrodes toward theelectrode support and the point of junction between the electrodeleading-in wire and the glass wall of the tube. destroying the glassinsulation at this point or cracking the wall of the tube. The

leading-in wires for passing current to the electrode of my tubeconsists of the pipes,

which are used to convey cooling fluid to the electrode and as thesepipes are maintained cool by the circulation of the fluid, thetemperature of the glass seal is maintained uniform and disintegrationdue to electrical discharge in the neighborhood of the seal isprevented, thus permitting the tube to be oper- I ated at very highpotentials and current densities without disintegration of theinsulating material and seal and the accompanying destruction of thetube. For example, in a tube of the half wave or rectifying type such asshown in Fig. 1 of the drawing. The current density of the smallelectrode might be run in the neighborhood of twenty-five amperes persquare decimeter of active area while the cooperating large electrode miht have such area as to operate at a current density of two or threeamperes per square decimeter without damage to the tube structure orserious attenuation of the gaseous atmosphere.

As tubes constructed in the manner which I have described above arecapable of operating at extremely high brilliancy due to the relativelyheavy current which can be passed through the tube, they are Welladapted for use in signalling purposes such as the guiding of aeroplanesand the like. A single tube or several tubes placed together form a veryconcentrated and very brilliant source of light which is visible for along distance at night. While any gas, such as one of the rare gases canbe used in these tubes, I prefer to use neon as this gas 'ves a light ofa very brilliant red color w ich when the tube is used for the guidingof aeroplanes is visible through fog for lon distances.

lVhile I have described for the purpose of illustration a particularembodiment of m invention, I do not wish to be limited thereto 'as otherchanges, obvious to one skilled in the art, can be made withoutdeparture from the spirit of the invention, as set forth in the appendedclaims.

What I claim is 1. In a gaseous discharge device, an electrodecomprising a conducting tube coiled in the form of a doublelielix andadapted to be traversed by a quantity of cooling fluid.

2. In an electrical dischargedevice an envelope, an elongated electrode,a heat resisting insulating sleeve surrounding the said.

electrode, a heat resisting tube surroundin said sleeve but slightlyspaced therefrom, the entire assembly being positioned within theenvelope, a lead-in wire sealed through the envelope and attached to theelectrode and a quantity of glass wool packed between the wall of theenvelope and the said heat resistingl tube for protecting said lead-inwire and sea In testimony whereof I have signed my name to thisspecification this 15th day of December, 1927;

WILLIAM F. HENDRY.

